Prostaglandin F2 alpha (PGF2 alpha) is luteolytic in vivo, but both luteolytic and luteotropic effects have been reported as in vitro effects. Previous work suggests that the luteotropic effects of PGF2 alpha observed with dispersed cell preparations of bovine corpora lutea is not a direct effect of PGF2 alpha, but is due to a metabolite. Therefore, we plan to identify this metabolite and determine its effects on cAMP and progesterone synthesis in vitro. The in vivo formation of this metabolite will be evaluated and its physiological significance relative to PGF2 alpha-induced luteolysis determined. Since a luteotropic metabolite of PGF 2 alpha may be formed as a consequence of PGF 2 alpha treatment, luteelytic effects of PGF 2 alpha only at the luteal cell level are difficult to accept. Accordingly, the temporal relationship between effects of PGF2 alpha on ovarian blood flow and ultrastructural characteristics, LH binding and steroidogenic response to LH will be determined. An attempt will be made to establish a cause and effect relationship between blood flow and luteolysis by changing the rate of in situ perfusion of the bovine ovary.